This invention relates to a rolling mill having a grooved roll such as a bar or wire rolling mill in which the dimensions of a rolling material are controlled.
One example of the arrangement of a successive rolling mill of this type is shown in FIG. 1.
The successive rolling mill comprises i stands. In FIG. 1, reference numeral 1 designates a mill stand; 2, a #2 stand; 3, a #i-1 stand; 4, a #i stand; and 5, the rolling material. The successive rolling mill in FIG. 1 is a so-called VH type rolling mill. That is, horizontal rolling machines (the odd-numbered stands in FIG. 1) and vertical rolling machines (the even-numbered stands in FIG. 1) are alternately arranged.
For instance, the #i-1 stand rolling machine 3 is a vertical rolling machine which carries out rolling in the direction X. In FIG. 1, reference character bi-1 designates the lateral width of the rolled material at the output of the #i-1 rolling machine, and reference character hi-1 designates the height thereof. The #i rolling machine is a horizontal rolling machine which carries out rolling in the direction Y. Reference character bi designates the lateral width at the output thereof, and reference character hi designates the height.
In a conventional successive rolling mill such as a bar or wire rolling mill, in order to reduce tension of the material between the stands equal to zero, loop control or a tension control mechanism has been employed. However, a successive rolling mill in which the dimensions of the rolling material are dynamically controlled has yet to be provided in the art because of the following reasons:
(1) The tolerances on the dimensions of the products have not been severe, and
(2) Elongation of the mill due to a variation in the load during rolling is small. (This reduces the effect of transmitting a variation of a rolling material at the input side to the delivery or output side, and therefore the accuracy of product dimension is not greatly varied.)
Thus, the conventional control is disadvantageous in that the dimensional accuracy is low, because, for example, the dimensional variation due to variations in the temperature of the rolling material is not controlled at all.